The present invention relates to a portable radio apparatus and more particularly to an illuminating device for a portable radio apparatus capable not only of selectively turning on or turning off illuminating means assigned to keys and a display in accordance with an environment around the apparatus, but also of adjusting an illumination to thereby save power as far as possible.
Today, portable radio apparatuses including handy phones and PHS (Personal Handyphone System) are extensively used and can be operated without regard to the environment, i.e., inside or outside of homes and offices. Generally, a portable radio apparatus includes LEDs (Light Emitting Elements) or similar illuminating device for facilitating user's operations even in darkness. The illuminating device, however, aggravates power consumption of the apparatus. This is a serious problem because many of portable radio apparatuses are powered by batteries.
In light of the above, Japanese Patent Laid-Open Publication No. 3-296123, for example, discloses a handy data terminal including switching means for selectively turning on or turning off power supply to a light source that illuminates display means at the back of the display means. Japanese Patent Laid-Open Publication No. 9-62198 teaches a display device included in a handy terminal for selectively turning on or turning off each of a plurality of display regions constituting an image display. These terminals each are constructed to turn off illumination in a daytime, outdoor environment in order to save power.
However, in parallel with the miniaturization of portable radio apparatuses and therefore that of batteries for powering them, there is an increasing demand for an illuminating device consuming even less power than the conventional illuminating devices.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 56-64523 and 61-26353 and Japanese Patent Laid-Open Publication Nos. 8-125730 and 9-247727.